Compositions, layerings, electrodes and methods for making

Abstract

There is a carbon-sulfur composite; and there is a composition comprising about 1 to 17.5 wt. % polymeric binder and about 50 to 99 wt. % carbon-sulfur composite comprising carbon powder having a surface area of about 50 to 4,000 square meters per gram and a pore volume of about 0.5 to 6 cubic centimeters per gram. The carbon powder comprises carbon having a macromolecular structure ordered in at least two dimensions and characterized by having two-dimensional carbon sheets which are stacked into carbon layers. The carbon-sulfur composite also comprises about 5 to 95 wt. % sulfur compound. There is also a layering comprising a plurality of coatings. Respective coatings in the plurality of coatings can comprise respective compositions. The respective coatings can comprise at least one polymeric binder and at least one carbon-sulfur composite comprising carbon powder and sulfur compound. There are also electrodes comprising a composition or a layering and methods of using such in cells.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority on and the benefit of the filing date of U.S. Provisional Application Nos. 61 / 587,817, filed on Jan. 18, 2012, and U.S. Provisional Application Nos. 61 / 597,915, filed on Feb. 13, 2012, the entirety of which is herein incorporated by reference.BACKGROUND OF THE INVENTION[0002]There is significant interest in lithium sulfur (i.e., “Li—S”) batteries as potential portable power sources for their applicability in different areas. These areas include emerging areas, such as electrically powered automobiles and portable electronic devices, and traditional areas, such as car ignition batteries. Li—S batteries offer great promise in terms of cost, safety and capacity, especially compared with lithium ion battery technologies not based on sulfur. For example, elemental sulfur is often used as a source of electroactive sulfur in a Li—S cell of a Li—S battery. The theoretical charge capacity associated with electroact...

AI Technical Summary

Benefits of technology

The patent text describes a new type of positive electrode for Li—S batteries that has a high capacity and is less likely to crack or break. This is achieved by using a composite of carbon and sulfur, which has a layering structure. These new positive electrodes also avoid low sulfur utilization and high discharge capacity degradation. This patent aims to improve the performance of Li—S batteries and provide them with better performance and durability.

Problems solved by technology

A common limitation of previously-developed Li—S cells and batteries is capacity degradation or capacity “fade”.

It is believed that the anode-deposited sulfur compounds can obstruct and otherwise foul the surface of the negative electrode and may also result in sulfur loss from the total electroactive sulfur in the cell.

However, simply utilizing a high loading of sulfur compound presents other difficulties, including a lack of adequate containment for the entire amount of sulfur compound in the high loading.

Furthermore, the positive electrodes made with these compositions tend to crack or break.

Another difficulty might be due, in part, to the insulating effect of the high loading of sulfur compound.

This insulating effect may contribute to difficulties in realizing the full capacity associated with all the potentially electroactive sulfur in the high loading in a positive electrode of these previously-developed Li—S cell and batteries.

However, a positive electrode incorporating a high binder amount tends to have a lower sulfur utilization which, in turn, lowers the effective maximum discharge capacity of the Li—S cells with these electrodes.

However, attaining the full theoretical capacities and energy densities remains elusive.

In addition, the concomitant limitations associated with capacity degradation, anode-deposited sulfur compounds and the poor conductivities intrinsic to sulfur compound itself, all of which are associated with previously-developed Li—S cells and batteries, limits the application and commercial acceptance of Li—S batteries as power sources.

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